Twin wire paper making method in which controlled dewatering in tapering gap causes suspension to move at speed of wires

ABSTRACT

Paper making method in which turbulent suspension under pressure is introduced to a tapering gap between a pair of traveling wires at the speed of the wires, and is dewatered therein by suction applied in a series of zones along the wires in such controlled manner that the quantity of liquid in the suspension decreases from zone-to-zone proportionally to gap width, and the suspension is caused to move through the gap at essentially the speed of the wires and without being subjected to substantial mechanical pressing by the wires.

United States Patent 1191 Arledter.

[ TWIN WIRE PAPER MAKING METHOD IN WHICH CONTROLLED DEWATERING INTAPERING GAP CAUSES SUSPENSION TO MOVE AT SPEED OF WIRES [76] Inventor:Hanns F. Arledter, Andritzer Reichsstrasse 122, 8046 Graz St. Viet,Austria [22] Filed:

Nov. 12, 1971 21 Appl. NO.I 198,304

[30] Foreign Application Priority Data Nov. 16, 1970 Austria 10273/70 52us. c1 162/203, 162/209, 162/211, 162/301, 162/303, 162/337, 162/341,162/342 51 11 1. c1. ..1)211 1/00 58 Field Of Search 162/203, 301, 303,374, 162/352, 337, 186, 209, 341, 357, 363, 323,

[56] References Cited UNITED STATES PATENTS 1,645,068 10/1927 OBrien162/301 2,046,271 6/1936 Lane et a1 162/323 X 3,103,463 9/1963 Justus162/341 3,149,028 9/1964 Robinson.. 162/303 3,403,073 9/1968 Moran162/203 3,438,854 4/1969 Means 162/374 X 1 Nov. 12, 1974 3,578,5615/1971 McCarrick et a1 162/352 1,241,905 10/1917 Behr 100/153 X1,875,075 8/1932 162/203 X 3,215,593 11/1965 Green 162/301 1 3,578,5585/1971 McCarrick et al.. 162/303 3,034,577 5/1962 Cirrito 162/3373,560,334 2/1971 Arledter [62/186 X 3,027,940 4/1962 Dunlap 162/363 XFOREIGN PATENTS OR APPLICATIONS 1,582,914 10/1969 France 162/2031,005,530 4/1952 France 1. 162/209 560,577 4/1944 Great Britain 162/341Primary Examiner-S. Leon Bashore Assistant Examiner-Richard 1-1. TushinAttorney, Agent, or Firm-Robert A. Ostmann [57] ABSTRACT Paper makingmethod in which turbulent suspension under pressure is introduced to atapering gap between a pair of traveling wires at the speed of thewires, and is dewatered therein by suction applied in a series of zonesalong the wires in such controlled manner that the quantity of liquid inthe suspension decreases from zone-to-zone proportionally to gap width,and the suspension is caused to move through the gap at essentially thespeed of the wires and without being subjected to substantial mechanicalpressing by the wires.

8 Claims, 4 Drawing Figures PATENTEUHGV 1 21974 3.847. 731

SHEEI I 0F 4 INVENTOR ATTORNEY PATENTEL W 1 3.847. 731

SNEEI 20$ 4 INVENTOR ATTORNEY PAH-INTEL HUV 1 21974 smt u gr 4 INVEN TORATTORNEY TWIN WIRE PAPER MAKING METHOD IN'WHICH CONTROLLED DEW'ATERINGIN TAPERING GAP CAUSES SUSPENSION TO MOVE AT SPEED OF WIRES BACKGROUNDOF THE INVENTION The invention relates to a paper making methodemploying a machine with two wires joining into a double wire area andconfining in front of said area a narrow converging gap for sheetforming.

Such machines are known. As other known paper making machines,suchmachines have the disadvantage that the formed sheet is composed oflayers with fibres orientated in the plane of said layers. Withincreasing wire speed and decreasing consistency of the suspension thelayers get more distinct. The single layers are badly connected to eachother. Besides, most of the fibres in the layers'are orientated in thedirection of wire travel, resulting in different strengths of the sheetin longitudinal and lateral direction.

Paper making method in which turbulent suspension under pressure isintroduced to a tapering gap between a pair of traveling wires at thespeedof the wires, and is dewatered therein by suction applied in aseries of zones along the wires in such controlled manner that thequantity of liquid in the suspension decreases from zone-to-zoneproportionally to gap width, and the suspension is caused to movethrough the gap at essentially the speed of the wires and without beingsubjected to substantial mechanical pressing by the wires.

SUMMARY OF THE INVENTION The purpose of the invention is to provide apaper making method in which the machine delivers in a wet process asheet having a fibre orientation distributed on all dimensionaldirections equally, and which can utilize high wire speeds.

According to the invention, atleast and preferably more than 50%, of webformation takes place in the converging gap, and the suspension is fedto the gap in a turbulent condition and under a pressure which causes itto enter at the speed of the wires. The suspension is dewatered bysuction applied in a series of zones positioned along the path of travelof each wire, and the degree of suction dewatering in each zone is setso that the quantity of liquid in the suspension decreases fromzone-to-zone in the direction of wire travel proportionally to the widthof the gap. This technique causes the suspension to move through the gapat essentially the speed of the wires and without being subjected toappreciable mechanical pressing by the wires.

The fibres coming in a turbulent suspension into the gap maintain theirorientation in all dimensional directions even during depositing on thewires. Good sheet quality is especially achieved if thequantities ofliquid to be sucked away in the zones, and/or the width of the gap is soadjusted that the suspension has reached the frozen condition at theoutlet of the gap. Under frozen condition is understood the conditionwherein the fibres cannot change their orientation because of the.

The gap definedby. thewires has a length of .300 to 2,000 mm, an inletwidth of 6 to mm, and anoutlet width of up to 5 mmrEach dewatering zonepreferably has a length, measured in thedirection of wire travel, of 60to mm, and is provided with a wire supporting surface having a radius ofcurvature of l,000mm to infinite. These zones are equipped with separatedevices foradjusting the quantities of liquid to besucked. away. It isof great advantage-if the dewatering ele ments are stationary suctionboxes having perforated wire supporting wallswhich are convex domedagainst the wires. Manufacturing costs are reduced if the surface of theconvex domed wall has the form of a cylin-. der section, the generatrixof which-is an arc of a circle. with a sector angle of less than 15. Thedomed walls guarantee, under thetension of the-wires, a smooth joiningof each wire to the surfacesof the boxes, resulting in a definitedistance between the wires and the boxes and minimal by-passing of air.Therefore, in each zone a definite vacuum can be established, and adefinite quantity of liquid can be sucked away.

For adjusting the machine in respect of the kind of suspension, the kindof sheet to be formed, or different wire speeds, advantageously thewidth of the inlet and- /or outlet of the gap is adjustable. Equally,the radius of curvature of the dewatering elements can be adjustable.For this purpose, the dewatering elements can be made of links turnableagainst each other, or can be.

substitutable by elements with another radius of curvation) of theelement is adjustable too.

Deposition of the fibres on the wires can be advantageously influenced,while maintaining equal speeds for suspension and wires, by hav-ing thequantity of liquid to be sucked away at one side of the gap bigger than,.at the other side of the gap, and then the quantity of liquid at theother side of the gap bigger than at the one side of the gap,alternating in directionof wire travel. The result is a suspensionflowing in the form of a serpentine through the gap.

Orientation of the fibres in the suspension can also be influenced byadjusting the quantities of liquid to be sucked away so as to have forone orsome zones a certain speed difference between suspension andwires. Neglecting this, that is taken essentially, the suspension iskept at the same speed as the wires.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the inventionv aredescribed herein in detail with reference to the accompanying drawingsin which:

FIG. 1 shows a vertical section, in the direction of wire travel,through a paper making machine FIG. 2 a corresponding vertical sectionthrough part of another embodiment, and

FIGS. 3 and 4 show each one form of a gap and dimensioning data forfurther gaps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The paper making machine shownin FIG. 1 has two wires 1 and 2 which join into a double wire area 3. Infront of the double wire area 3, .immediatly before the. wires 1, 2joininto area 3 the wires 1, 2 form a converging gap 4 between themselves.The length of the gap 4 is 300 to 2,000 mm. The width of the gap 4 is atthe inlet 4 of the gap 6 to 100 mm, and the width of the gap is at itsoutlet 4 some tenth of millimeter to 5 mm. The wires 1 and 2 travel overdewatering elements 5 and 6, respectively, arranged on both sides of thegap 4. The dewatering elements are subdivided into a plurality of zones,i.e. into zones 7, 9, l1, l3, l5 and 8, 10, 12, l4, 16, respectively.Each of the zones has an adjusting device-not shownfor adjusting thequantity of the liquid to be sucked away in the respective zone.Dewatering elements 17 and 18, arranged in front of the inlet 4 alsoeach have an adjusting device-mot shown-for adjusting the liquid to besucked away. The dewatering elements can be moved-by means notshownrelatively to each other so as to make the width of the gap 4 atthe inlet 4 or at the outlet 4 bigger or smaller.

A chamber 19 for feeding suspension to the gap 4 opens against the inlet4, i.e. the lower end of gap 4. This chamber 19 has two feeding conduits20, 21 arranged symmetrically to the gap 4, and a return conduit 22, forthe suspension.

The inlet width (4) of the gap 4 and the pressure of the suspension tobe lead to the gap 4 are so adjustable as to make the speed of thesuspension at the inlet 4 equal to the speed of the wires 1, 2. Thequantities of liquid to be sucked away with the zones 7 to 16 are soadjustable as to make the speed of the suspension along the gap, i.e.from the inlet 4 to the outlet 4 essentially equal to the speed of thewires 1, 2. Thereby, the quantities of liquid to be sucked away with thezones and/or the width of the gap 4 are so adjustable as to have reachedat least at the outlet 4 of the gap 4 a consistency at which thesuspension is in the frozen condition.

The dewatering elements 17, 18 at the transition between chamber 19 andinlet 4 are formed as stationary suction boxes with a perforatedwire-supporting convex domed wall. In the chamber 19 are insertedturbulence generators, i.e. rotatable perforated rollers 23, 24,rotatable bodies 25, 26 and a rotatable cylinder 27.

An element of the chamber 19, that is the wall of said chamber can beset under oscillations with periodic frequencies of more than 5 persecond, by a vibrator 28. Similarly, vibrators 29 and 30 serve foroscillating the dewatering elements 5 and 6, respectively with periodicfrequencies of more than 50 per second. The direction of oscillating isat an angle of at least degress relatively to the plane of the wires,i.e. as for the vibrator 28 an angle of 30, and for the vibrators 29 and30 an angle of 90.

The suspension has in the chamber 19 practically constant consistency.1n the gap 4, the consistency increases with short fibre lengths (1 to 6mm) from 0.1 to 1.5% at the inlet 4 up to 3 to 6% at the outlet 4 Withlong fibre lengths (6 to 30 mm), the consistency increases from 0.001 to0.1% at the inlet 4 up to 0.5 to 1% at the outlet 4 Thereby, with theinvention, very high wire speeds can be achieved, even with the higherconsistencies.

1n the double wire area 3 in which the two wires 1, 2 support the formedsheet at both sides, the dewatering process can be brought up to 44%consistency, i.e. solids per solids plus liquid, with the help of boxes31 having perforated wire-supporting convex domed walls, groovedcylinders 32, and a pair of cylinders 33.

The gap 4 is arranged vertical and converges in direction of wire travelfrom below to above. The suspension flows upward in the gap 4.

With the embodiment according to FIG. 2, the gap 4 is arrangedvertically too, yet the gap converges downwards, and the suspensionflows downwards. The chamber for feeding the suspension to the gap 4 isformed as a box 34 the bottom of which is formed by the wires 1 and 2.1n the box 34, a bath of suspension is maintained. Under the box 34,suction boxes 35 and 36 are arranged. Part of sheet forming takes placeon the wires 1, 2 before these wires enter the gap 4. The layer of thesheet lying between the layers formed in box 34 are then formed in gap 4according to the invention.

The quantities of liquid to be sucked away in the zones of the gap 4 areso adjusted as to make the speed of the suspension along the gapessentially equal to the speed of the wires. Maintaining this condition,alternating from zone to zone in the direction of wire travel, firstly,at one side of the gap 4 is sucked away a bigger quantity of liquid thanat the other side of the gap 4, then at said other side of the gap issucked away a bigger quantity of liquid than at the one side of the gap,then in the, in the direction of wire travel, third zone vice versa.That is, the quantity in zone 7 is bigger than in zone 8, in zone 10bigger than in zone 9, in zone 11 bigger than in zone 12, in zone 14bigger than in zone 13, in zone 15 bigger than in zone 16. The stream ofsuspension in gap 4 gets therefore the form of a serpentine.

For acting on the fibres in the direction of flow, the quantities ofliquid to be sucked away in the zones are so adjusted that with a pairof zones, i.e. with the zones 9 and 10, a difference of speeds betweensuspension and wires occurs. Such a local acceleration or retardationcould be repeated in further pairs of zones. Especially if acceleratedand retarded zone pairs alternate, the speed of the suspension can be ingeneral kept equal to the speed of the wires all the same.

The ends of the dewatering elements 5 and 6 are staggered relatively toeach other at the outlet 4 of gap 4. This is advantageous with smallwidths of the outlet 4 With the box 34, more than two feeding and/orreturn conduits open into it, that is the feeding conduits 37 and 38,and the return conduits 39 and 40. The kind of sheet forming in the box34 as well as the condition of the suspension delivered to the gap 4 canthereby be influenced.

The walls of the dewatering elements 5 and 6 are lightly convex domedagainst the wires, and have the form of a cylinder section thegeneratrix of which is an arc of circle with a big radius. The surfaceof the convex domed wall is made of a material having a coefficient offriction of smaller than 0.1 relatively to a wire made of metal.

With the gaps given with FIG. 3 the sketch at the left side of thedrawing shows an inlet width d an outlet width d and a length 1 of thegap. The gap is in the drawing confined by two arcs of circle, each ofthem reaching from the inlet to the outlet of the gap, and having aradius r and a sector angle a. The gap is subdivided-into twelve zonesof equal length. At the right hand of the sketch, a table gives theportion of the liquid to be sucked away, which is left in the suspensionat the end of each zone (in of the total quantity of liquid to be suckedaway in the whole gap) for four different forms of gap. The length l ofthe gaps is equal with all forms, namely 1,200 mm, while the differenced between inlet width d and outlet width d as well as the radius 'r andthe corresponding sector angle a are different. 5 by the invention.

FIG. 4 corresponds to FIG. 3. Yet, the length 1 of the Table 6 ShowsProduction capacities for p p made gaps i 500 mm d th gaps are bdi id di fi of synthetic fibres, dependent on fibre lengths and corzones. Thereare seven different forms of gaps. responding consistencies of theSuspension With the shown forms of gaps, the table given quancomblhlhgTables 2 to 5 Ph can See P- hh f tity of liquid decreases in thedirection of wire travel 10 hohs of m of the Speed qhahthy Ofhqhld fromzone to zone proportionally to the width of the to be Shcked hl lehgthof the-suction e and gap The diff between the total quantity (100%)productlon capacity are a function of the consistency and the quantitygiven in the table has to be sucked of the h h' away at the respectivezone end. This way the speed of Suspensions with ng fibres fortion-woven webs can the Suspension in the gap is constant AS tomake'this be dewatered according to the lnventlon with wire speedexactly constant, the perforations of the suction Speeds of 1,000 to1,200 m P mlhute, fh at the boxes can differ with a zone in thedirection of wire Inlet, of the gap of 40 to 70 h and quamltles of have]in respect of form and/Or Size pension of 48,000 to 70,000l1terpermlnute and lateral With the gap forms according to FIG. 3, the totalh of the Sheet quantity f liquid to be Sucked away in the gap is Withshort fibre suspensions, wire speeds of 1,000 to 40,000, with the FIG. 4forms 30,000,liter per minute 1,500 m Per Ihlhhtei h at the 1hlet of theg and meter lateral width f the Sheet of 20 mm, the production of paperwith the machine In order tofeed the suspension into the gap 4 withacicordlhg to the Invention reaches 100 to 300 kg P wire speed thesuspension has to be fed to the chamber mlhhte i m lateral Width of theSheet 19 with a pressure that is higher than the pressure cor- The Wldthat the hlet 41 of the gap 4 has he f responding to wire speed. Table 1shows the respective than the length of thehhres; As Shown thls Cohdl'pressures (meter water column) for some wire speeds hoh can he metwhhthe lhvehhoh- (meter per minute). Under paper making machlne andpaper is also The width (mm) of the inlet 1 of the gap 4 is a funcunderstood, in the sense of th s specification, a mation of the quantityof suspension (liter per minute and Chlhe Produces a paper'hke Sheet forexample meter lateral width of the sheet) flowing through the a machhefor pmdhc'hg hoh'woveh websgap and of the wire speed. For equal'speedsof suspension and wires, Table 2 shows some examples. TABLES:

In Table 3, the production of paper (Kilogramm per Table 1 minute andmeter lateral width of the sheet, or metric tons per 24 hours and meterlateral width of the sheet) S d Inlet Pressure Inlet Pressure for isgiven as a function of consistency (per cent) and hf as? 4 (m WC)Chamber WC) quantity of suspension flowing through the gap.

The production of the machine according to the in- 40 88 ventionfurthermore-depends on the degree of freeness, 600 610 the dewateringorsuction area, the weight of square 900 meter of paper, and thedewateringvacuum or suction 2M pressure. Dewatering on the double wire system,that is from two sides of the-sheet, and up to consistencies of l to 6%results in big quantities of liquid sucked away. In Table 4,'thequantities (liter/per minute and Table 2 square meter suction area) aregiven for some kinds of suspension, dependent on different suctionpressures Quantity of Liquid (llmin/m) (meter water column). hi onwidths d (mm) of Table 5 shows for a suction box with planewiresupporting wall (radius of curvature being infinite) and 10 20 40 alength Of 1 meter, subdivided into 10 zones, the quan- 1500 15 000 30()00 0 000 9() 000 112 000 tity of liquid to be sucked away witheachzone. With 1000 lo 000 20 000 40 000 60 000 75 000 1 meter lateral widthof the sheet, each zone has a suc- 55 tion area of 1,000 cm The quantityof liquid (liter per 500 5 000 10 000 20 000 30 000 37 500 minute) isgiven dependent on wire speed (meter per 250 2 500 5 000 I0 000 15 000I8 750 minute) and width d (mm) of the gap. A

Table 3 Consist- Production (kg/min/m) above (to/24 hours/m) cncy onQuantities of Suspension (l/min/m) of By adjusting the width d ofthe-gap (10 bis mm) and the suction pressure (2 to 8 m water column),any quantities of liquid to be sucked away with the production of thedifferent paper quanlities are easily coped Table 3 Continued Consist-Production (kg/min/m) ahovc (to/24 hours/m) ency (Cl 1 on Quantities ofSuspension (l/min/m) of Table 4 20 a pair of traveling wires, the methodcomprising the steps of Material Quantity of Liquid (l/min/m) a.establishing and maintaining, in a region ad acent S r P WC f the gapinlet, a volume of fiber suspension which 15 on "assure m )0 underpressure, has uniform consistency, and is in 5 a turbulent state,

Nomwoven 60 000 I20 000 b. sa1d pressure bemg such as to causesuspens1on to flow 1nto the gap at the speed of the w1res;

40 c. causing the wires to pass in contact with suspen- Low Freenesssion in sa1d reg1on 1mmed1ately before they define P111, with 20 000 40000 60000 Said Mcdium Freeness d w1thdraw1ng l1qu1d from the suspenslon1n sa1d req n j 000 20 000 30 gion through each wire by suction tothereby cause deposition of fibers on the wires and effect partial Pulpwith Very 2 000 4 000 0 000 formation of the sheet;

e. withdrawing liquid from the suspension in the gap through each of thewires by suction applied in each of a series of separate zonespositioned along Table 5 the path of travel of the wire, whereby theconsis- 40 tency of the suspension increases gradually as the WireOuamjrg p q l g R Zone suspension travels through the gap and a sheet is2323, m lea formed therefrom between the two wires; and

on W1dths d of f. setting the degree of suction dewatering effected in80 60 40 20 0 each zone so that the quantlty of l1qu1d 1n thesuspens1ondecreases from zone-to-zone 1n the d1rec- 1200 600 tion of wire travelproportionally to the width of L000 4000 3000 2000 1000 500 the gap, andthe suspension is caused to move 00 7400 I600 800 400 through the gap atessent1ally the speed of the w1res and without being subjected toappreciable me- 000 2400 I800 1200 600 300 chanical pressing by thewires. 400 600 1200 800 400 200 2. A method as defined ln cla m 1 1nwh1ch a. w1thdrawal of sa1d l1qu1d 1n the gap 15 effected through twosets of suction boxes having perfo- T rated wire-supporting walls whichare convex able 6 domed agalnst the w1res, H, L h C t P d I, b. wherebycontact between the w1res and the walls C C I) C I)" l t rp ""21(kg/mink; (w/day/m) mmimiz es by-passmg of a r 1nto sa1d boxesand1nsures w1thdrawal of defimte quantlties of l1qu1d 1n 3 10 0 0.100 48.068.0 Said Zones 0 m 10 0.050 24.0 34.0 3. A method as defined in claim 1in which a. th uantities of li 'd wi h w h t 10 m 15 0.020 14.0 20.8 tdra n throug he two w1res 1n each zone are unequal; and 10 to 30 0.0053.5 b. in adjacent zones the greater quantity is withdrawn throughdifferent wires, c. whereby the suspension in the gap has a tendency Iclaim: to form a serpentme.

l. A paper making method in which at at least 30% of the forming of acontinuous sheet is effected by dewatering a fiber suspension in atapered gap defined by 4. A method as defined in claim 1 including thestep of continuously circulating suspension through said region betweena plurality of feeding and return conduits.

5. A method as defined in claim 1 including the step of vibratingsuspension in said region at a frequency greater than 5 cycles persecond.

6. A method as defined in claim 1 including the step of vibratingsuspension in the gap at a frequency greater than 50 cycles per second.

1. A PAPER MAKING METHOD IN WHICH AT LEAST 30% OF THE FORMING OF ACONTINUOUS SHEET IS EFFECTED BY DEWATERING A FIBER SUSPENSION IN ATAPERED GAP DEFINED BY A PAIR OF TRAVELING WIRES, THE METHOD COMPRISINGTHE STEPS OF A. ESTABLICHING AND MAINTAINING, IN A REGION ADJACENT THEGAP INLET, A VOLUME OF FIBER SUSPENSION WHICH IS UNDER PRESSURE, HASUNIFORM CONSISTENCY, AND IS IN A TURBULENT STATE, B. SAID PRESSURE BEINGSUCH AS TO CAUSE SUSPENSION TO FLOW INTO THE GAP AT THE SPEED OF THEWIRES; C. CAUSING THE WIRES TO PASS IN CONTACT WITH SUSPENSION IN SAIDREGION IMMEDIATELY BEFORE THEY DEFINE SAID GAP; D. WITHDRAWING LIQUIDFROM THE SUSPENSION IN SAID REGION THROUGH EACH WIRE BY SUCTION TOTHEREBY CAUSE DEPOSITION OF FIBERS ON THE WIRES AND EFFECT PARTIALFORMATION OF THE SHEET; E. WITHDRAWING LIQUID FROM THE SUSPENSION IN THEGAP THROUGH EACH OF THE WIRES BY SUCTION APPLIED IN EACH OF A SERIES OFSEPARATE ZONES POSITIONED ALONG THE PATH OF TRAVEL OF THE WIRE, WHEREBYTHE CONSISTENCY OF THE SUSPENSION INCREASES GRADUALLY AS THE SUSPENSIONTRAVELS THROUGH
 2. A method as defined in claim 1 in which a. withdrawalof said liquid in the gap is effected through two sets of suction boxeshaving perforated wire-supporting walls which are convex domed againstthe wires, b. whereby contact between the wires and the walls minimizesby-passing of air into said boxes and insures withdrawal of definitequantities of liquid in said zones.
 3. A method as defined in claim 1 inwhich a. the quantities of liquid withdrawn through the two wires ineach zone are unequal; and b. in adjacent zones the greater quantity iswithdrawn through different wires, c. whereby the suspension in the gaphas a tendency to form a serpentine.
 4. A method as defined in claim 1including the step of continuously circulating suspension through saidregion between a plurality of feeding and return conduits.
 5. A methodas defined in claim 1 including the step of vibrating suspension in saidregion at a frequency greater than 5 cycles per second.
 6. A method asdefined in claim 1 including the step of vibrating suspension in the gapat a frequency greater than 50 cycles per second.
 7. A method as definedin claim 6 in which the suspension in the gap is vibrated in a planeforming an angle of at least 20* with the planes of the wires.
 8. Amethod as defined in claim 1 in which turbulence in said region isproduced mechanically by a rotating body.